The invention relates to an applicator for applying a liquid impregnation agent to running yarns.
In an applicator known from EP 0 619 262 a leaf spring is responsible for the permanent contact by which a wick is pressed in the contact area against the surface of the applicator element, particularly independent from the current height adjustment of the applicator element, the height position of which can be varied in order to vary the wrapping angle of the yarn. The surface of the applicator element is smooth. During its rotation, contaminants such as fiber parts of the yarn, dust and the like are stripped off from the surface. During operation of the applicator unavoidable flying lint is also collected there, such that finally at the entrance of the contact area gradually a large pad of impurities is formed which shows a significant absorbing effect. Impregnating agent conveyed by the transfer member into the contact area increasingly is absorbed by the capillary effect of said pad, resulting in an uncontrollable, strong impregnation consumption and a fading wetting of the surface which in the worst case even runs dry.
From EP 0 080 843 A a device for lubricating yarn material is known in which a transfer roller directly running in a lubrication liquid bath has chevron-like grooves at its surface. Said chevron-shaped grooves serve to uniformly distribute the lubricant over the surface of the transfer roller and to uniformly apply the lubricant to the yarn. Impurities originating from the yarn material and flying lint collect in the lubricant bath which quickly gets dirty. Moreover, due to the chevron-shaped grooves the yarn is impregnated only intermittently.
From DE 802 665 A a device is known for treating yarn with a liquid during spooling on a bobbin. Said device has a rotatable applicator roller in line contact with the surface of the bobbin. A liquid tank and a wick are associated with said applicator roller. A drive system controls periodical contact between the surface of the roller and said wick to prevent the wick from becoming too hot or to prevent too much liquid from being brought onto the roller in order to thereby adapt the treatment intensity to the properties of the liquid and yarn.
Further prior art related to applicators is contained in DE 41 13 339 A; DE 28 03 488 A; U.S. Pat. Nos. 3,053,222 A; 4,845,964 A; DE 540 244 A.
It is an object of the invention to improve an applicator of the kind as disclosed at the beginning such that the consumption of the liquid impregnating agent remains substantially constant and as adjusted. Furthermore, even during long operation duration uniform impregnation of the yarn material ought to be achieved. Operation disturbance by impurities ought to be prevented. By uniform low consumption a low maintenance frequency for the applicator ought to be achieved.
The above object is achieved by providing the applicator with an onboard or integrated cleaning device for impurities collecting between the transfer member and an applicator element.
The onboard or integrated cleaning device of the applicator is activated during operation of the applicator. The cleaning device then removes impurities having the tendency to increasingly collect in the contact area between the transfer member and the applicator element, and hinders in a preventive way the formation of a contamination pad which could absorb the impregnation agent. The consumption of impregnation agent remains as adjusted and uniform even for long periods of operation. The yarn is impregnated uniformly. The applicator only seldom needs maintenance. In other words the premature operation of the cleaning device suppresses the formation of an absorbing pad of critical size of lost yarn material and collected contamination in the contact area, because contamination is removed from the entrance of the contact area during the operation of the applicator.
In a preferred embodiment, the applicator is in the form of a roller and a stripper member is periodically brought in stripping engagement at the transfer member which is in the form of an elastic wick-like body, such that the stripper member has the function of a catch and conveys collected contamination out of the critical area between the body and the roller.
In a further embodiment, a lifting member serves to temporarily lift at least the body from the surface of the roller counter to the force of a spring loading the body, such that impurities are conveyed away while bonding to the surface or, alternatively, by the influence of the stripper member directly. In such cases, it may be sufficient to only lift the body a little bit or to make it at least forceless such that impurities may slip through. The lifting member may rotate with the roller so that it simultaneously serves as a catch and to lift the body. It is possible not to move the lifting member by the roller but to separate the lifting member from the roller and to let it engage from outside at the body or at the spring loading of the body.
In a further embodiment, stripper member is in the form of at least one projection protruding from the surface of the applicator element in strips to clean the critical contact area. Since this takes place at least once with each full revolution of the roller, no absorbing pad of fiber materials and impurities will be formed.
A further embodiment involves the projection being formed as a rod-like body, such as a pin or a tube embedded into the roller. In this embodiment, the roller is simple to manufacture with the pin or the tube and the rotating roller (either driven by the running yarn or by its own drive system) provides the driving energy for the projection which in turn does the cleaning work.
In an alternative embodiment, the edge region of a depression formed into the surface of the applicator element or roller serves as the stripper member. Said edge portion carries impurities away and cleans the body. The depression has the effect that the frequently somewhat elastic and compacted impurities tend to locally expand into the depression and are caught and more easily taken away by the edge region.
The projection and/or the depression in the surface of the roller is at least substantially parallel to the axis of the roller. Other geometrical configurations or orientations might be expedient as well (oblique, chevron-like, punctually, etc.). Neither the projection nor the edge region have to extend laterally across the entire surface, and it may be sufficient to only provide shorter sections thereof with interspaces. These sections even might be offset in the circumferential direction with respect to one another.
In a further embodiment, the stripper member simultaneously defines the lifting member. During the cleaning process a combination effect is achieved since the stripper member conveys contamination away like a catch while it also lifts the body at least temporarily from the surface to more easily carry impurities away.
In this case, it is expedient to use the applicator element as the rotary drive for the lifting member and/or stripper member. The cleaning device then does not need its own drive.
Alternatively, in a further embodiment a drive is provided for the lifting member and/or the stripper member for moving the respective member periodically through the contact area and to carry away impurities and/or to lift a transfer member at the same time.
For embodiments in which the lifting member and/or the stripper member is/are not driven by the roller itself, pneumatic, electric or electromagnetic drive systems may be provided which engage by suitable auxiliary assemblies at said body or at the spring which loads said body, to temporarily strip or lift.
In a further embodiment,the spring is made of magnetic material and repelling magnetic forces are employed to temporarily lift the body from the surface. The magnet is received within the roller and fulfills a lifting step during each revolution to clean the contact area and to prevent the formation of an undesirable pad.
In a further embodiment the spring is pulled back by means of a temporarily excitable stationary magnet to relieve the body for a short while or to totally lift it from the surface such that impurities are conveyed away.
A lifting member and/or stripper member rotating with the roller may influence the yarn under certain operation conditions. It could cause e.g. a pulsation of the yarn tension or the yarn itself. In order to avoid such effects, a smooth yarn contact portion may be provided where the lifting and/or stripper member does not become active for the yarn. A sufficiently effective cleaning effect nevertheless occurs, as in the impurities, particularly fiber materials, a physical and mechanical bonding effect is present by which the stripper member when only partially engaging at a fiber collection will nevertheless carry away such impurities from the contact area.
It is of particular importance for the invention that the applicator has an onboard or integrated cleaning device which is at least periodically active during the operation of the applicator and which carries away impurities which tend to collect in the critical entrance of the contact area between the applicator element and the transfer member. This is expediently done by a stripper member and/or a lifting member rotating with the applicator roller to carry away impurities during each revolution of the roller and to lift the transfer member from the applicator element for an easy removal of the impurities. Due to the active influence of the cleaning device the applicator operates with continuous and precisely adjustable consumption of the impregnation agent. The yarn is impregnated very uniformly and economically. This also results in a low maintenance frequency for refilling the applicator. The formation of a large absorbing impurity and yarn material pad is suppressed by preventively and periodically removing small impurity depositions.